Effects of tubular daylight guidance systems on the daylighting performance and energy savings in office buildings under different climate zones

Abstract

Over the recent years, the energy use of artificial lighting has been gradually increasing in office buildings. Tubular daylight guidance system (TDGS) is an innovative daylighting technology, which is used to transport daylight into the core of a building. In this study, the effects of the tube radius of TDGSs, window-to-wall ratio (WWR), and window orientation on the indoor illuminance, artificial lighting electricity consumption, and heating/cooling loads of an office room are investigated for the five climate zones in China by both numerical simulations and experiments. The model is developed using Radiance and Ecotect, and its feasibility is validated by comparing the simulated indoor illuminance distributions with the field measurements. The results demonstrate that the increase in the tube radius and the decrease in the WWR and the utilization of a north-facing window can improve the daylighting performance and energy savings of the TDGSs. In general, the TDGSs can reduce the artificial lighting electricity consumption and heating load while increasing the cooling load of the office room. Due to the implementation of TDGSs, the maximum potential energy savings (on the lighting energy use and the heating/cooling energy use) are 27.6% in Kunming (moderate climate), 13.5% in Chengdu (hot summer and cold winter), 10.6% in Guangzhou (hot summer and warm winter), 10.3% in Beijing (cold), and 5.0% in Harbin (severe cold).